CN113115405B

CN113115405B - Apparatus and method for signaling system information

Info

Publication number: CN113115405B
Application number: CN202110449333.2A
Authority: CN
Inventors: 阿尼尔·阿基瓦尔; 张泳彬
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2016-02-29
Filing date: 2017-02-27
Publication date: 2022-02-01
Anticipated expiration: 2037-02-27
Also published as: US11924883B2; CN113115404A; CN113115404B; EP3809791A1; EP3409048A1; KR20180111873A; US10455621B2; KR102677234B1; EP3409048A4; US20190132884A1; US20170251500A1; US20240215076A1; CN108605268B; AU2017227408B2; JP2022171797A; US20220124823A1; JP7143216B2; AU2017227408A1; EP3809791B1; EP4195860A1

Abstract

The present disclosure relates to a communication method and system for fusing a 5 th generation (5G) communication system and internet of things (IoT) technology, the 5 th generation communication system for supporting higher data rates beyond a 4 th generation (4G) system. The present disclosure may be applied to intelligent services based on 5G communication technologies and IoT related technologies, such as smart homes, smart buildings, smart cities, smart cars, networked cars, healthcare, digital education, smart retail, security and security services. A method for receiving System Information (SI) by a User Equipment (UE) in a wireless communication system is provided. The method includes receiving, from a Base Station (BS), a first type SI associated with SIs necessary for communication with the BS, and receiving, from the BS, a second type SI associated with at least one SI required by a UE.

Description

Apparatus and method for signaling system information

The present application is a divisional application entitled "apparatus and method for signaling system information" filed on 2017, 27/2, application No. 201780009548.4.

Technical Field

The present disclosure relates to wireless communication systems. More particularly, the present disclosure relates to an apparatus and method for transmitting and receiving system information.

Background

To meet the increasing demand for wireless data services since the deployment of fourth generation (4G) communication systems, much effort has been made to develop improved fifth generation (5G) or quasi-5G (pre-5G) communication systems. Accordingly, the 5G or quasi-5G communication system is also referred to as a "super 4G network" or a "Long Term Evolution (LTE) system". The 5G communication system is considered to be implemented in a higher frequency (millimeter wave) band (for example, 60GHz band) in order to achieve a higher data rate. In order to reduce propagation loss of radio waves and increase transmission distance, beamforming, massive Multiple Input Multiple Output (MIMO), full-dimensional MIMO (FD-MIMO), array antenna, analog beamforming, large antenna technology are discussed in the 5G communication system. Further, in the 5G communication system, development of system network improvement is being performed based on advanced small cells, cloud Radio Access Network (RAN), ultra-dense network, device-to-device (D2D) communication, wireless backhaul, mobile network, cooperative communication, coordinated multipoint (CoMP), reception-side interference cancellation, and the like. In 5G systems, hybrid Frequency Shift Keying (FSK) and Quadrature Amplitude Modulation (QAM) modulation (FQAM) and Sliding Window Superposition Coding (SWSC) have been developed as Advanced Coding Modulation (ACM), and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and Sparse Code Multiple Access (SCMA) as advanced access techniques.

The internet, which is a human-oriented connected network where humans generate and consume information, is now constantly evolving into the internet of things (IoT), where distributed entities, such as things, exchange and process information without human intervention. Internet of everything (IoE) has emerged through a combination of IoT technology and big data processing technology connected with cloud servers. Since IoT implementations require technical elements such as "sensing technology", "wired/wireless communication and network infrastructure", "service interface technology", and "security technology", sensor networks, machine-to-machine (M2M) communication, Machine Type Communication (MTC), etc. have recently been studied. Such an IoT environment can provide an intelligent internet technology service that creates new value for human life by collecting and analyzing data generated between connected things. Through the fusion and combination of existing Information Technology (IT) and various industrial applications, IoT can be applied to a variety of fields including smart homes, smart buildings, smart cities, smart cars or networked cars, smart grids, healthcare, smart home appliances, and advanced medical services.

In line with this, various attempts have been made to apply the 5G communication system to the IoT network. For example, techniques such as sensor network, MTC, and M2M communication may be implemented through beamforming, MIMO, and array antennas. The application of cloud radio access networks (cloud RANs), which are the big data processing technologies described above, can also be considered as an example of the convergence between 5G technologies and IoT technologies.

In recent years, several broadband wireless technologies have been developed to meet the growing number of broadband users and to provide more and better applications and services. Second-generation wireless communication systems have been developed to provide voice services while ensuring mobility of users. Third generation wireless communication systems support not only voice services but also data services.

In recent years, a fourth wireless communication system has been developed to provide high-speed data services. However, fourth generation wireless communication systems currently lack resources to meet the ever-increasing demand for high-speed data services. Accordingly, fifth generation wireless communication systems are being developed to meet the increasing demand for high speed data services, support ultra-reliable and low latency applications, and support large-scale machine type communication.

In fourth generation wireless communication systems, enhanced node BS (enbs) or Base Stations (BSs) in a cell broadcast system information. The system information is constructed as a Master Information Block (MIB) and a set of System Information Blocks (SIBs). The MIB consists of a System Frame Number (SFN), a downlink system bandwidth, and a physical hybrid automatic repeat request (ARQ) feedback indicator channel (PHICH) configuration. The MIB is transmitted once every 40 ms. It repeats every 10ms, where the first transmission occurs in subframe #0 when SFM mod 4 equals zero. The MIB is transmitted on a physical broadcast channel. SIB type 1 carries cell indemnity, tracking area code, cell barring information, value tag (common to all scheduling units) and scheduling information for other SIBs. When SFN mod 8 equals zero, SIB1 is transmitted every 80ms in subframe # 5. When SFN mod 2 equals zero, SIB1 repeats in subframe # 5. SIB1 is transmitted on the physical downlink shared channel. Other SIBs (SIB 2 to SIB 19) are transmitted in a System Information (SI) message, with the scheduling information of these SIBs indicated in SIB 1. SIBs with the same periodicity may be transmitted in one SI message. The SI message is broadcast on the physical downlink shared channel. Various SIBs, their use and conventional sizes are shown in table 1 below.

TABLE 1.4 System information in G systems

A User Equipment (UE) acquires system information at cell selection, cell reselection, after handover is completed, after entering evolved UMTS terrestrial radio access (E-UTRA) from another Radio Access Technology (RAT), upon re-entering a service area, upon receiving a notification (page), and upon exceeding a maximum validity period (3 hours).

In the Radio Resource Control (RRC) idle state, the UE needs to acquire MIB, SIB1, SIB 2 to SIB 5, SIB 6 to SIB 8 (depending on the supported RAT), SIB 17 (if LTE-Wireless Local Area Network (WLAN) is supported) Interworking (IWK), and SIB 18 to SIB19 (if D2D is supported). In the RRC connected state, the UE needs to acquire MIB, SIB1, SIB 2, SIB 8 (depending on the supported RAT), SIB 17 (if LTE-WLAN IWK is supported), and SIB 18 to SIB19 (if D2D is supported). The acquired and stored system information is considered invalid if the value tag in the received SIB1 is different from the value tag in the stored SI.

The system information may be changed and notified as follows: the change is notified by a paging message (in RRC _ IDLE or RRC _ CONNECTED), where a system information notification is caused to let the UE know that a certain SI is changing in the next modification period. The modification period boundary is SFN-dependent, such that SFN mod modification period is 0. The change of SI occurs at a specific radio frame. The notification of the change in modification period N will be reflected in N + 1. The SIB1 also carries a value tag to indicate the modification of the SI. The UE discovers the change in SI by looking at the value tag in SIB1 or receiving a page with system information modification at the end of the modification period (if the check page is missed).

The above information is presented merely as background information to aid in understanding the present disclosure. No determination is made and no assertion is made as to whether any of the above is available as prior art with respect to the present disclosure.

Disclosure of Invention

Technical problem

One of the problems in the current method of transmitting system information using a Master Information Block (MIB)/System Information Block (SIB) is whether or not a User Equipment (UE) is in a cell; if any UE in the cell needs the information, MIB/SIB is broadcasted periodically. In the case of small cell deployment, it is unnecessary to regularly broadcast all these SIBs and results in a significant waste of resources and increased energy consumption.

Next generation communication systems are considering carrier frequency ranges up to 100 GHz. At higher frequencies, beamforming is essential to compensate for path loss. One transmission beam cannot provide complete cell coverage. Multiple transmission beams are required. In order to broadcast system information, it is necessary to transmit the system information using a plurality of transmission beams by switching Transmission (TX) beams across a plurality of slots. The overhead (time/frequency resources) of transmission of system information using beamforming is N times the transmission of system information without beamforming, where "N" is the number of transmission beams. Transmission resources remaining after resources are consumed for transmitting system information may be used for data scheduling for users in the direction of a Downlink (DL) transmission beam. Thus, if more time/frequency resources are consumed for transmitting system information, user data scheduling becomes restrictive and inflexible.

In addition, when the UE moves from one cell to another cell, the UE must re-acquire system information. This results in increased power consumption by the mobile UE. There is therefore a need for an enhanced method of signaling system information.

Solution to the problem

Aspects of the present disclosure are directed to solving at least the above problems and/or disadvantages and to providing at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide a method for receiving System Information (SI) by a UE in a wireless communication system. The method comprises the following steps: receiving, from a Base Station (BS), a first type SI associated with an SI necessary for communication with the BS; transmitting a Physical Random Access Channel (PRACH) preamble to the BS based on the first type SI; receiving a Random Access Response (RAR) message from a BS; and receiving a second type SI associated with at least one SI required by the UE from the BS.

According to an aspect of the present disclosure, there is provided a method for transmitting System Information (SI) by a Base Station (BS) in a wireless communication system. The method comprises the following steps: transmitting, to a User Equipment (UE), a first type of SI associated with an SI necessary for communication with the UE; receiving a Physical Random Access Channel (PRACH) preamble from a UE based on a first type SI; sending a Random Access Response (RAR) message to the UE; and transmitting, to the UE, a second type SI associated with at least one SI required by the UE.

According to an aspect of the present disclosure, there is provided a User Equipment (UE) for receiving System Information (SI) in a wireless communication system. The UE includes: a transceiver configured to transmit and receive signals; and at least one processor configured to: controlling reception of a first type of SI associated with an SI necessary for communication with a Base Station (BS) from the BS; controlling to transmit a Physical Random Access Channel (PRACH) preamble to a BS based on a first type SI; controlling reception of a Random Access Response (RAR) message from a BS; and controlling reception of the second type SI associated with at least one SI required by the UE from the BS.

According to an aspect of the present disclosure, there is provided a Base Station (BS) for transmitting System Information (SI) in a wireless communication system. The BS includes: a transceiver configured to transmit and receive signals; and at least one processor configured to control sending, to a User Equipment (UE), a first type of SI associated with SIs necessary for communication with the UE; controlling receiving, from a UE, a Physical Random Access Channel (PRACH) preamble based on a first type of SI; controlling sending a Random Access Response (RAR) message to the UE; and controlling transmission of the second type SI associated with at least one SI required by the UE to the UE.

Advantageous effects of the invention

According to an aspect of the present disclosure, there is provided a User Equipment (UE) and a BS. The UE and the BS can efficiently signal system information in a wireless communication system.

Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure.

Drawings

The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings in which:

fig. 1 illustrates a method for obtaining system information according to an embodiment of the present disclosure;

fig. 2 illustrates a method for classifying system information parameters into System Information Blocks (SIBs) according to an embodiment of the present disclosure;

figure 3 illustrates a method for classifying system information parameters into SIBs according to an embodiment of the present disclosure;

fig. 4 illustrates a method for classifying system information parameters into a system information set, according to an embodiment of the present disclosure;

fig. 5 illustrates a method for classifying system information parameters into a system information set according to another embodiment of the present disclosure;

fig. 6 illustrates a method for obtaining system information according to another embodiment of the present disclosure;

fig. 7 illustrates a method for obtaining system information according to another embodiment of the present disclosure;

fig. 8 illustrates a method for obtaining system information according to another embodiment of the present disclosure;

fig. 9 illustrates a method for obtaining system information according to another embodiment of the present disclosure;

fig. 10 illustrates a method for indicating whether other system information is broadcast in basic system information that is broadcast according to an embodiment of the present disclosure;

fig. 11 illustrates a method for obtaining system information according to another embodiment of the present disclosure;

fig. 12 illustrates a method for indicating whether other system information is broadcast in basic system information that is broadcast according to another embodiment of the present disclosure;

fig. 13 illustrates a method for obtaining system information according to another embodiment of the present disclosure;

fig. 14 illustrates a method for acquiring system information according to another embodiment of the present disclosure;

fig. 15 illustrates a method for acquiring system information according to another embodiment of the present disclosure;

fig. 16 illustrates a method for providing system information within a time window according to an embodiment of the present disclosure;

fig. 17 illustrates a method for providing system information by monitoring a time window for one or more periods of time, according to an embodiment of the present disclosure;

fig. 18 illustrates a method for configuring a system information area ID according to an embodiment of the present disclosure;

fig. 19 illustrates a method for indexing system information parameters according to an embodiment of the present disclosure; and is

Fig. 20 illustrates a method for configuring a system information configuration Identity (ID) according to an embodiment of the present disclosure.

Throughout the drawings, the same reference numerals will be understood to refer to the same parts, components and structures.

Detailed Description

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure as defined by the claims and their equivalents. It includes various specific details to aid understanding, but these are to be considered exemplary only. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Moreover, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the written meaning, but are used only by the inventors to enable a clear and consistent understanding of the disclosure. Accordingly, it will be apparent to those skilled in the art that the following descriptions of the various embodiments of the present disclosure are provided for illustration only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "component surface" includes reference to one or more such surfaces.

Fig. 1 illustrates a method for acquiring system information according to an embodiment of the present disclosure.

Referring to fig. 1, in an embodiment of the present disclosure, a User Equipment (UE) may acquire system information, as shown in fig. 1. System Information (SI) is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information and/or transmission, routing and packet (TRP) information that is periodically broadcast by a cell. The second class (also referred to as other SIs) includes one or more system information that is provided on demand or that may be broadcast periodically.

The first class includes basic system information such as information required for initial access to a cell, information required for acquisition of system information in the second class. The first type of system information includes at least a System Frame Number (SFN), a list of Public Land Mobile Network (PLMN) Identities (IDs), a cell ID, a cell camping parameter, etc. The second type of system information includes system information not included in the first type. The first type (also referred to as minimum SI or basic SI) of system information is broadcast by the cell and/or TRP periodically.

In operation S110, the UE acquires a first class (also referred to as a minimum SI or a basic SI) from the broadcast information. Whether the system information in the second category is broadcast periodically or provided on demand, the network signal is in the first category of system information, i.e., in the minimum SI or the basic SI.

For example, where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast, while the small cell may indicate that system information is not broadcast. In another example, if there are several requests for on-demand system information, the network may start broadcasting system information instead of providing system information on-demand.

The minimum SI or the basic SI may include an indication that all SIs of the second type of system information are periodically broadcast or provided on demand. Alternatively, the minimum SI or basic SI may include a separate indication for each SI (e.g., System Information Block (SIB)) or set of SIs (i.e., SIBs), where each indication indicates whether to periodically broadcast or provide the associated SI or set of SIs on demand.

Alternatively, the minimum SI or the basic SI may include a separate indication for each SI message, where each SI message carries one or more SIs (i.e., multiple SIBs). The indication associated with the SI message indicates whether to broadcast or provide the SI associated with the SI message on an as-needed basis. The mapping of SI messages to SIBs is included in the minimum SI or the basic SI.

To acquire the second type SI, the UE first determines whether to broadcast the SI periodically or to provide the SI on demand. The UE determines this based on an indication included in the first type (also referred to as minimum SI or basic SI) of system information. In operation S110, if the first type (also referred to as minimum SI or basic SI) system information indicates that the SI that the UE wants to acquire is periodically broadcast (or not provided on demand), the UE acquires the SI from the periodic broadcast using scheduling information included in the first type (also referred to as minimum SI or basic SI). If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is not regularly broadcasted (or provided on demand), the UE sends a request to a Base Station (BS) to receive the SI.

In order to receive one or more system information provided on demand, the UE transmits a random access Preamble (PRACH) in operation S120. In one embodiment, the PRACH preamble or PRACH opportunity (i.e., time/frequency resources) used to request system information may be different from the PRACH preamble or PRACH opportunity used for other purposes. This may minimize the impact on the random access load due to the SI request. The PRACH preamble or PRACH opportunity (i.e., time/frequency resources) for acquiring system information may be predefined or signaled by the network in a first type (also referred to as minimum SI or basic SI) of system information.

Upon receiving the random access preamble, the BS transmits a Random Access Response (RAR), and the RAR includes an Uplink (UL) grant for transmitting the SI request message in operation S130. The RAR may also include a timing advance and/or a push-back indicator and/or a preamble identifier (identifying the PRACH preamble).

The UE verifies that the RAR corresponds to the PRACH sent by it. If the verification is successful, the UE transmits an SI request message in a UL grant in operation S140. The SI request message indicates one or more system information (e.g., SIBs) required by the UE, or indicates one or more sets of system information required by the UE, or indicates a service (e.g., enhanced mobile broadband (eMBB), Mobile Telecommunications Company (MTC), ultra-reliable and low latency (URLL), etc.) or a UE type in which the UE requires the system information. The UE may send its UE ID (i.e., SAE-temporary mobile subscriber identity (S-TMSI), cell-radio network temporary identifier (C-RNTI), random access-radio network temporary identifier (RA-RNTI), etc.), as well as the SI request message.

In response to the SI request, the BS transmits an SI response, wherein the SI response includes the requested system information, in operation S150. The SI response may be broadcast or provided in a unicast manner. The scheduling control information indicating the SI response may be masked with an ID of the UE (e.g., C-RNTI, RA-RNTI) or a predefined ID (e.g., system information-radio network temporary identifier (SI-RNTI)). The predefined ID may be different for different system information or system information sets or services or UE types.

After sending the SI request, one or more SIs (i.e., SIBs) requested by the UE are provided within some time window (i.e., SI response window). After sending the SI request, the UE listens to a new radio-physical downlink control channel (NR-PDCCH) in the SI response window in order to receive the requested SIB. The UE may retransmit the SI request if the UE does not receive the requested SIB within the SI response window. The length of the SI response window is provided in the minimum SI or the basic SI. Alternatively, after sending the SI request, to receive the requested SIB, the UE monitors the SI window of the requested SIB in one or more SI periods of the SIB. Scheduling information for other SIs, including SIB type, validity information, periodicity, SI window information, may be provided at the minimum SI, regardless of whether other SIs are periodically broadcast or provided on demand. In one embodiment, the UE first checks the SI response window for SI response and, if not received, it monitors the SI window to receive the requested SI.

In one embodiment, an evolved node b (enb) may provide requested system information for one or more cells and/or TRPs. The ENB may indicate a cell and/or a TRP to which the system information provided in the SI response is applicable. Therefore, when the UE changes cell and/or TRP, the UE does not need to request system information. After the cell and/or TRP change, if the UE does not have system information of the new cell and/or TRP, the UE requests the system information.

In another embodiment of the present disclosure, the BS may indicate the supported SI in the basic system information. The UE may then request one or more supported SIs to be provided on demand using the previously explained method (fig. 1). In one embodiment, a default configuration of system information may be defined, which the UE uses until they are obtained from the cell.

In another embodiment, a cell may broadcast some SI in the first type of system information. The remaining SI in the first type system information of a cell may be broadcast or provided according to the needs of another cell. In the request, the UE may include information about the cell (e.g., cell ID, frequency, cell index, etc.) for which the SI is requested.

The UE may indicate the required system information in the SI-request using one of the following options (option 1 to option 5):

option 1:

figure 2 illustrates a method for classifying system information parameters into SIBs according to an embodiment of the present disclosure.

Referring to fig. 2, the system information parameters are classified into SIBs. In the SI request, a bitmap of size N bits is included, where each bit corresponds to one SIB. The bit corresponding to the SIB may be set to one to indicate that the SIB is needed by the UE, or may be set to zero to indicate that the SIB is needed by the UE. Alternatively, the UE may include a list of SIBs in the SI request instead of a bitmap.

Option 2:

figure 3 illustrates a method for classifying system information parameters into SIBs according to another embodiment of the present disclosure.

Referring to fig. 3, the system information parameters are classified into SIBs. The SIBs are then grouped into SIB sets (or SI messages), where each set includes one or more SIBs.

SIBs may exist in more than one set of SIBs. Grouping SIBs into SIB sets may be done based on service (e.g., mobile broadband (MBB), URLL, Mobile Telecommunications Company (MTC), device to device (D2D), D2D-discovery, D2D-communication, vehicle to outside world (V2X), vehicle to vehicle (V2V), etc.) or UE type (MTC UE, MBB UE, D2D UE, etc.).

In the SI request, a bitmap of size P bits is included, where each bit corresponds to a set of SIBs. A bit corresponding to the SIB set may be set to one to indicate that the SIB is needed for the UE. Alternatively, the UE may include a list of SIB sets in the SI request instead of the bitmap.

Option 3:

fig. 4 illustrates a method for classifying system information parameters into a system information set according to an embodiment of the present disclosure.

Referring to fig. 4, system information parameters are classified into a system information set. Grouping system information parameters into system information sets may be done based on service (e.g., MBB, URLL, MTC, D2D, D2D-discovery, D2D-communication, V2X, V2V, etc.) or UE type (MTC UE, MBB UE, D2D UE, etc.). In the SI request, a bitmap of size P bits is included, where each bit corresponds to a system information set. A bit corresponding to a system information set may be set to one to indicate that the UE needs the system information set. Alternatively, the UE may include a list of SI sets in the SI request instead of the bitmap.

Option 4:

fig. 5 illustrates a method for classifying system information parameters into a system information set according to another embodiment of the present disclosure.

Referring to fig. 5, there is a predefined mapping between one or more system information parameters and a service. In the SI request, a bitmap of size N bits is included, where each bit corresponds to a service. A bit corresponding to a service may be set to one to indicate that the UE needs system information for the service. Alternatively, the UE may include a list of one or more services in the SI request instead of a bitmap, where each service may be identified by a service type.

Option 5:

in this method, the UE may indicate the UE type in the SI request. The UE type indicates the services supported by the UE. There is a predefined mapping between one or more system information parameters and a service. Accordingly, upon receiving the SI request having the UE type, the BS can know system information parameters required by the UE.

Fig. 6 illustrates a method for acquiring system information according to another embodiment of the present disclosure.

Referring to fig. 6, in another embodiment of the present disclosure, a UE may acquire system information, as shown in fig. 6. System information is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information that is periodically broadcast by a cell and/or TRP. The second category (also referred to as other SIs) includes one or more system information that is provided to the UE on demand or that may be broadcast periodically.

The first class includes basic system information such as information required for initial access to a cell, information required for acquisition of system information in the second class. The first type of system information includes at least SFN, list of PLMN IDs, cell ID, cell camping parameters, etc. The second type of system information includes system information not included in the first type.

The first type (also referred to as minimum SI or basic SI) of system information is regularly broadcast by the cell and/or TRP. In operation S610, the UE acquires first-type (also referred to as minimum SI or basic SI) system information from broadcast information. Whether the system information in the second category is broadcast periodically or provided on demand, the network signal is in the first category of system information, i.e., in the minimum SI or the basic SI.

For example, where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast, while the small cell may indicate that system information is not broadcast. In another example, if there are several requests for on-demand system information, the network may start broadcasting system information instead of providing system information on-demand. The minimum SI or the basic SI may include an indication that all SIs of the second type of system information are periodically broadcast or provided on demand.

Alternatively, the minimum SI or basic SI may include a separate indication for each SI (e.g., SIB) or set of SIs (i.e., SIBs), where each indication indicates whether to periodically broadcast or provide the associated SI or set of SIs on demand.

Alternatively, the minimum SI or the basic SI may include a separate indication for each SI message, where each SI message carries one or more SIs (i.e., multiple SIBs). The indication associated with the SI message indicates whether to broadcast or provide the SI associated with the SI message on an as-needed basis. The mapping of SI messages to SIBs is included in the minimum SI or the basic SI. To acquire the second type SI, the UE first determines whether to broadcast the SI periodically or to provide the SI on demand. The UE determines this based on an indication included in the first type (also referred to as minimum SI or basic SI) of system information.

If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is periodically broadcast (or not provided on demand), the UE acquires the SI from the periodic broadcast using scheduling information included in the first type (also referred to as minimum SI or basic SI) of system information. If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is not regularly broadcasted (or provided on demand), the UE sends a request to the BS to receive the SI.

In order to receive one or more system information provided on demand, the UE transmits a random access preamble in operation S620. In one embodiment, the PRACH preamble or PRACH opportunity (i.e., time/frequency resources) used to request system information may be different from the PRACH preamble or PRACH opportunity used for other purposes. This may minimize the impact on the random access load due to the SI request. The PRACH preamble or PRACH opportunity (i.e., time/frequency resources) for acquiring system information may be predefined or signaled by the network in a first type (also referred to as minimum SI or basic SI) of system information.

Upon receiving the random access preamble, the BS transmits a RAR, and the RAR includes a UL grant for transmitting the SI request message in operation S630. The RAR may also include a timing advance and/or a push-back indicator and/or a preamble identifier (identifying the PRACH preamble).

The UE verifies that the RAR corresponds to the PRACH sent by it. If the verification is successful, the UE transmits an SI request message in an UL grant in operation S640. The UE may not indicate which system information the UE needs. The bearer on which the UE sends the SI request supports one service. The UE indicates that it needs system information. The BS provides system information for the services supported on the bearer. There may be a predefined mapping between bearers and services.

Alternatively, the supported services may be indicated in a first type (also referred to as minimum SI or basic SI) of system information. In operation S650, the SI response may be broadcast or provided in a unicast manner. The scheduling control information indicating the SI response may be masked with the ID of the UE (e.g., C-RNTI, RA-RNTI) or a predefined ID (e.g., SI-RNTI). The predefined ID may be different for different system information or system information sets or services or UE types.

After sending the SI request, one or more SIs (i.e., SIBs) requested by the UE are provided within some time window (i.e., SI response window). After sending the SI request, the UE listens to the NR-PDCCH in the SI response window in order to receive the requested SIB. The UE may retransmit the SI request if the UE does not receive the requested SIB within the SI response window.

The length of the SI response window is provided in the minimum SI or the basic SI. Alternatively, after sending the SI request, to receive the requested SIB, the UE monitors the SI window of the requested SIB in one or more SI periods of the SIB. Scheduling information for other SIs, including SIB type, validity information, periodicity, SI window information, may be provided at the minimum SI, regardless of whether other SIs are periodically broadcast or provided on demand. In one embodiment, the UE first checks the SI response window for SI response and, if not received, it monitors the SI window to receive the requested SI.

In one embodiment, the eNB may provide the requested system information for one or more cells and/or TRPs. The ENB may indicate a cell and/or a TRP to which the system information provided in the SI response is applicable. Therefore, when the UE changes cell and/or TRP, the UE does not need to request system information. After the cell and/or TRP change, if the UE does not have system information of the new cell and/or TRP, the UE requests the system information.

In another embodiment of the present disclosure, the BS may indicate the supported SI in the basic system information. The UE may then request one or more supported SIs using the previously explained method (fig. 6). In one embodiment, a default configuration of system information may be defined, which the UE uses until they are obtained from the cell.

Fig. 7 illustrates a method for acquiring system information according to another embodiment of the present disclosure.

Referring to fig. 7, in the method of the present disclosure, a UE may acquire system information, as shown in fig. 7. System information is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information that is periodically broadcast by a cell and/or TRP. The second category (also referred to as other SIs) includes one or more common system information that is provided to the UE on demand or that may be broadcast periodically.

The first class includes basic system information such as information required for initial access to a cell, information required for acquisition of system information in the second class. The first type of system information includes at least SFN, list of PLMN IDs, cell ID, cell camping parameters, etc. The second type of system information includes system information not included in the first type. The first type (also referred to as minimum SI or basic SI) of system information is regularly broadcast by the cell and/or TRP. In operation S710, the UE acquires first-type (also referred to as minimum SI or basic SI) system information from the broadcast information.

Whether the system information in the second category is broadcast periodically or provided on demand, the network signal is in the first category of system information, i.e., in the minimum SI or the basic SI. For example, where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast, while the small cell may indicate that system information is not broadcast. In another example, if there are several requests for on-demand system information, the network may start broadcasting system information instead of providing system information on-demand. The minimum SI or the basic SI may include an indication that all SIs of the second type of system information are periodically broadcast or provided on demand. Alternatively, the minimum SI or basic SI may include a separate indication for each SI (e.g., SIB) or set of SIs (i.e., SIBs), where each indication indicates whether to periodically broadcast or provide the associated SI or set of SIs on demand.

Alternatively, the minimum SI or the basic SI may include a separate indication for each SI message, where each SI message carries one or more SIs (i.e., SIBs). The indication associated with the SI message indicates whether to broadcast or provide the SI associated with the SI message on an as-needed basis. The mapping of SI messages to SIBs is included in the minimum SI or the basic SI. To acquire the second type SI, the UE first determines whether to broadcast the SI periodically or to provide the SI on demand. The UE determines this based on an indication included in the first type (also referred to as minimum SI or basic SI) of system information.

The second type of system information may be further classified into common system information and non-common system information. The common system information includes one or more SIs (i.e., SIBs) required by each UE regardless of the features or services in which they are interested. The non-common system information includes one or more SIs (i.e., SIBs) that are not required by each UE. These SIs are feature or service specific (e.g., SIBs related to D2D, MTC, V2V, V2X, multimedia broadcast/multicast service (MBMS), etc.).

In order to receive one or more SIs provided on demand, the UE transmits a random access preamble in operation S720. The PRACH preamble or PRACH opportunity (i.e., time/frequency resources) used to acquire system information may be different from the PRACH preamble or PRACH opportunity used for other purposes. The PRACH preamble or PRACH opportunity to acquire system information may be predefined or signaled by the network in a first type (also referred to as minimum SI or basic SI) of system information.

Upon receiving the random access preamble, the BS transmits a Random Access Response (RAR), and the RAR may include an UL grant for transmitting a system information request message in operation S730. The RAR includes common system information. The RAR may also include a timing advance and/or a push-back indicator and/or a preamble identifier (identifying the PRACH preamble).

The UE verifies that the RAR corresponds to the PRACH sent by it. If the verification is successful, the UE may transmit an SI request message in an UL grant to request one or more system information according to its needs in operation S740. The SI request message indicates system information or a system information set or a service or a UE type. The UE may send its UE ID (i.e., S-TMSI, C-RNTI, RA-RNTI, etc.) along with the SI request message. In response to the SI request, the ENB transmits an SI response, wherein the SI response includes the requested system information, in operation S750.

The scheduling control information indicating the SI response may be masked with the ID of the UE (e.g., C-RNTI, RA-RNTI) or a predefined ID (e.g., SI-RNTI). The predefined ID may be different for different system information or system information sets or services or UE types. The UE may indicate the required system information in the SI-request using the options explained in the description of method 1.

In one embodiment, based on the PRACH preamble, the content of the RAR may be one of:

1. common system information and no UL grant: this is the case when the UE only needs the common SI.

2. Common system information and UL grant: this is the case when the UE needs a common SI and some other SI. This is also the case when the UE needs the common SI and wants to send some other RRC message (e.g. connection request, connection resume request, etc.) after receiving the RAR.

UL grant: this is the case when the UE does not need any SI or when the UE does not need common system information but needs some other SI.

For each of the above cases, the PRACH preamble and/or the PRACH opportunity may be different. The PRACH preamble or PRACH opportunity to acquire system information for each of these cases may be predefined or signaled by the network in a first type (also referred to as minimum SI or basic SI) of system information.

The UE selects the appropriate PRACH preamble and/or PRACH opportunity accordingly. For example, the UE may only require common system information. If the UE only needs common system information, it indicates to the eNB using the appropriate PRACH preamble and/or PRACH opportunity. The PRACH preamble and/or PRACH opportunity for this purpose is different from other purposes. In this case, the UE will not send the SI request after receiving the RAR.

In another scenario, the UE needs common system information and also wants to request additional system information. In this case, the UE needs common system information and UL grant in the RAR. The UE indicates to the eNB using the appropriate PRACH preamble and/or PRACH opportunity. The PRACH preamble and/or PRACH opportunity for this purpose is different from other purposes. In this case, the UE will send the SI request after receiving the RAR. In another scenario, the UE may want to request system information and need UL grant in the RAR. The UE indicates to the eNB using the appropriate PRACH preamble and/or PRACH opportunity. The PRACH preamble and/or PRACH opportunity for this purpose is different from other purposes.

In another embodiment of the present disclosure, the BS may indicate the supported SI in the basic system information. The UE may then request one or more supported SIs using the previously explained method (fig. 7).

Fig. 8 illustrates a method for acquiring system information according to another embodiment of the present disclosure.

Referring to fig. 8, in the method of the present disclosure, a UE may acquire system information, as shown in fig. 8. System information is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information that is periodically broadcast by a cell and/or TRP. The second category (also referred to as other SIs) includes one or more common system information that is provided to the UE on demand or that may be broadcast periodically.

The first type (also referred to as minimum SI or basic SI) of system information is regularly broadcast by the cell and/or TRP. In operation S810, the UE acquires first-type (also referred to as minimum SI or basic SI) system information from broadcast information.

Whether the system information in the second category is broadcast periodically or provided on demand, the network signal is in the first category of system information, i.e., in the minimum SI or the basic SI. For example, where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast, while the small cell may indicate that system information is not broadcast. In another example, if there are several requests for on-demand system information, the network may start broadcasting system information instead of providing system information on-demand. The minimum SI or the basic SI may include an indication that the SI indicating the second type of system information is periodically broadcast or provided on demand. Alternatively, the minimum SI or basic SI may include a separate indication for each SI (e.g., SIB) or set of SIs (i.e., SIBs), where each indication indicates whether to periodically broadcast or provide the associated SI or set of SIs on demand.

In order to receive one or more system information provided on demand, the UE transmits a random access Preamble (PRACH) in operation S820. The PRACH preamble and/or PRACH opportunity used to acquire system information in the RAR may be different from the PRACH preamble and/or PRACH opportunity used for other purposes.

In an embodiment of the present disclosure, upon receiving a random access preamble, the BS transmits a RAR in operation S830. The random access preamble acts as an SI request in this approach. The RAR includes SI responses, i.e. common system information.

In one embodiment, the UE may use dedicated signaling to acquire other system information specific to its needs (e.g., the UE may enter a connected state and request system information from the eNB in a dedicated manner). In alternative embodiments, the SI response may be broadcast or provided in a unicast manner upon receiving the random access preamble for the SI. The scheduling control information indicating the SI response may be masked with the ID of the UE (e.g., C-RNTI, RA-RNTI) or a predefined ID (e.g., SI-RNTI). The predefined ID may be different for different system information or system information sets or services or UE types. After sending the SI request, one or more SIs (i.e., SIBs) requested by the UE are provided within some time window (i.e., SI response window). After sending the SI request, the UE listens to the NR-PDCCH in the SI response window in order to receive the requested SIB.

The UE may retransmit the SI request if the UE does not receive the requested SIB within the SI response window. The length of the SI response window is provided in the minimum SI or the basic SI. Alternatively, after sending the SI request, to receive the requested SIB, the UE monitors the SI window of the requested SIB in one or more SI periods of the SIB.

Scheduling information for other SIs, including SIB type, validity information, periodicity, SI window information, may be provided at the minimum SI, regardless of whether other SIs are periodically broadcast or provided on demand. In one embodiment, the UE first checks the SI response window for SI response and, if not received, it monitors the SI window to receive the requested SI.

In embodiments where the SI response is broadcast in the SI window instead of or in the RAR, the RAR may still be sent to acknowledge successful reception of the SI request. In embodiments where the SI response is broadcast in the SI window instead of the SI response window or in the RAR, an indication may be included in the minimum SI to indicate that the BS successfully received the SI request.

In one embodiment, an eNB may provide system information for one or more cells and/or TRPs. The ENB may indicate a cell and/or a TRP to which the system information provided in the RAR is applicable. Therefore, when the UE changes cell and/or TRP, the UE does not need to request system information. After the cell and/or TRP change, if the UE does not have system information of the new cell and/or TRP, the UE requests the system information.

In another embodiment of the present disclosure, the BS may indicate the supported SI in the basic system information. The UE may then request one or more supported SIs using the previously explained method (fig. 8).

Fig. 9 illustrates a method for acquiring system information according to another embodiment of the present disclosure.

Referring to fig. 9, in the method of the present disclosure, a UE may acquire system information, as shown in fig. 9. System information is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information that is periodically broadcast by a cell and/or TRP. The second category (also referred to as other SIs) includes one or more common system information that is provided to the UE on demand or that may be broadcast periodically.

The first type (also referred to as minimum SI or basic SI) of system information is regularly broadcast by the cell and/or TRP. In operation S910, the UE acquires first-type (also referred to as minimum SI or basic SI) system information from the broadcast information.

Whether the system information in the second category is broadcast periodically or provided on demand, the network signal is in the first category of system information, i.e., in the minimum SI or the basic SI. For example, where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast, while the small cell may indicate that system information is not broadcast.

In another example, if there are several requests for on-demand system information, the network may start broadcasting system information instead of providing system information on-demand. The minimum SI or the basic SI may include an indication that the SI indicating the second type of system information is periodically broadcast or provided on demand. Alternatively, the minimum SI or basic SI may include a separate indication for each SI (e.g., SIB) or set of SIs (i.e., SIBs), where each indication indicates whether to periodically broadcast or provide the associated SI or set of SIs on demand.

Alternatively, the minimum SI or the basic SI may include a separate indication for each SI message, where each SI message carries one or more SIs (i.e., SIBs). The indication associated with the SI message indicates whether to broadcast or provide the SI associated with the SI message on an as-needed basis. The mapping of SI messages to SIBs is included in the minimum SI or the basic SI. To acquire the second type SI, the UE first determines whether to broadcast the SI periodically or to provide the SI on demand.

The UE determines this based on an indication included in the first type (also referred to as minimum SI or basic SI) of system information. If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is periodically broadcast (or not provided on demand), the UE acquires the SI from the periodic broadcast using scheduling information included in the first type (also referred to as minimum SI or basic SI). If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is not regularly broadcasted (or provided on demand), the UE sends a request to the BS to receive the SI.

In order to receive one or more system information provided on demand, the UE transmits a random access preamble (PRACH-SI) in operation S920. The random access preamble acts as an SI request in this approach. The PRACH preamble and/or PRACH opportunity used to acquire system information in the RAR may be different from the PRACH preamble and/or PRACH opportunity used for other purposes.

In one embodiment, the PRACH-SI preamble used to acquire system information in the RAR is predefined. In this option, the PRACH time/frequency resource may be one of the following:

alt 1: fixed with respect to PSS/SSS/BCH/SFN 0

Alt 2: providing in basic system information

Alt 3: using conventional PRACH time/frequency resources

In another embodiment, the PRACH-SI preamble used to acquire system information in the RAR is not predefined. The UE may use any PRACH preamble. In this option, the PRACH time/frequency resource is specific to the PRACH-SI and may be one of the following:

alt 1: fixed with respect to PSS/SSS/BCH/SFN 0

Alt 2: providing in basic system information

The UE determines the PRACH-SI transmission power using one of the following options:

alt 1: open loop power control similar to PRACH

Alt 2: transmitting at maximum power

Alt 3: configuring transmission power

Upon receiving the PRACH-SI, the BS transmits RAR in operation S930. The RAR includes other system information. In alternative embodiments, the SI response may be broadcast or provided in a unicast manner upon receiving the random access preamble of the SI. The scheduling control information indicating the SI response may be masked with the ID of the UE (e.g., C-RNTI, RA-RNTI) or a predefined ID (e.g., SI-RNTI). The predefined ID may be different for different system information or system information sets or services or UE types.

After sending the SI request, one or more SIs (i.e., SIBs) requested by the UE are provided within some time window (i.e., SI response window). After sending the SI request, the UE listens to the NR-PDCCH in the SI response window in order to receive the requested SIB. The UE may retransmit the SI request if the UE does not receive the requested SIB within the SI response window. The length of the SI response window is provided in the minimum SI or the basic SI.

Alternatively, after sending the SI request, to receive the requested SIB, the UE monitors the SI window of the requested SIB in one or more SI periods of the SIB. Scheduling information for other SIs, including SIB type, validity information, periodicity, SI window information, may be provided at the minimum SI, regardless of whether other SIs are periodically broadcast or provided on demand. In one embodiment, the UE first checks the SI response window for SI response and, if not received, it monitors the SI window to receive the requested SI. In embodiments where the SI response is broadcast in the SI window instead of or in the RAR, the RAR may still be sent to acknowledge successful reception of the SI request.

In embodiments where the SI response is broadcast in the SI window instead of the SI response window or in the RAR, an indication may be included in the minimum SI to indicate that the BS successfully received the SI request.

In one embodiment, the eNB may provide the requested system information for one or more cells. The ENB may indicate a cell to which the provided system information is applicable. Therefore, when the UE changes cells, the UE does not need to request system information. After the cell change, if the UE does not have system information of the new cell, the UE requests the system information.

In another embodiment of the present disclosure, the BS may indicate the supported SI in the basic system information. The UE may then request one or more supported SIs using the previously explained method (fig. 9).

Fig. 10 illustrates a method for indicating whether other system information is broadcast in basic system information that is broadcast according to an embodiment of the present disclosure.

Referring to fig. 10, system information (in addition to basic system information) may also be broadcast by the BS in an embodiment of the present disclosure. As shown in fig. 10, the BS may indicate whether other system information is broadcast in the broadcasted basic system information. If not broadcasted, the UE may request using the previously explained method (FIG. 9).

In operation S1010, the BS periodically broadcasts minimum/basic system information (e.g., sets SI _ TX _ Indication to zero). In operations S1020 and S1030, when the SI _ TX _ Indication is set to zero, the UE transmits PRACH-SI to acquire other system information. In operation S1040, the BS transmits an SI-response/RAR-SI including other system information in response to the PRACH-SI.

In operation S1050, the BS periodically broadcasts minimum/basic system information (e.g., sets SI _ TX _ Indication to one). In operation S1060 and operation S1070, when the SI _ TX _ Indication is set to one, the UE acquires other system information from broadcast signaling.

If broadcasted, the UE reads the broadcasted system information to acquire required system information. In the case where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast (e.g., set SI _ TX _ Indication to one), and the small cell may indicate that system information is not broadcast (e.g., set SI _ TX _ Indication to zero).

In one embodiment, the SI TX Indication may be signaled for each SI or set of SIs in the minimum/basic system information.

In one embodiment, the BS may provide the requested system information for one or more cells. The ENB may indicate the cell to which the system information provided in the RAR-SI applies. Therefore, when the UE changes cells, the UE does not need to request system information. After the cell change, if the UE does not have system information of the new cell, the UE requests the system information.

Fig. 11 illustrates a method for acquiring system information according to another embodiment of the present disclosure.

Referring to fig. 11, in the method of the present disclosure, a UE may acquire system information, as shown in fig. 11. System information is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information that is periodically broadcast by a cell and/or TRP. The second category (also referred to as other SIs) includes one or more common system information that is provided to the UE on demand or that may be broadcast periodically.

The first class includes basic system information such as information required for initial access to a cell, information required for acquisition of system information in the second class. The second type of system information includes system information not included in the first type.

The first type (also referred to as minimum SI or basic SI) of system information is regularly broadcast by the cell and/or TRP. In operation S1110, the UE acquires first-type (also referred to as minimum SI or basic SI) system information from the broadcast information.

In order to receive other system information, the UE transmits a random access preamble (PRACH-SI) in operation S1120. The random access preamble acts as an SI request in this approach. The PRACH preamble and/or PRACH opportunity used to acquire system information in the RAR may be different from the PRACH preamble and/or PRACH opportunity used for other purposes.

The PRACH preamble and/or PRACH opportunity for each SI (i.e., SIB) or set of SIs (i.e., SIBs) may be predefined or signaled in a first class (also referred to as minimum SI or basic SI). In one embodiment, the PRACH-SI preamble used to acquire system information in the RAR is predefined.

The PRACH-SI preamble may be specific to system information or a set of system information or a service or a UE type. In this option, the PRACH time/frequency resource may be one of the following:

alt 1: fixed with respect to PSS/SSS/BCH/SFN 0

Alt 2: provided in the basic system information. This may be specific to system information or a set of system information or service or UE type.

Alt 3: using PRACH time/frequency resources

alt 1: fixed with respect to PSS/SSS/BCH/SFN 0

alt 1: open loop power control similar to PRACH

Alt 2: transmitting at maximum power

Alt 3: configuring transmission power

Upon receiving the PRACH-SI, the BS sends RAR in operation S1130. The RAR includes the requested system information. In alternative embodiments, the SI response may be broadcast or provided in a unicast manner upon receiving the random access preamble of the SI. The scheduling control information indicating the SI response may be masked with the ID of the UE (e.g., C-RNTI, RA-RNTI) or a predefined ID (e.g., SI-RNTI). The predefined ID may be different for different system information or system information sets or services or UE types.

Alternatively, after sending the SI request, to receive the requested SIB, the UE monitors the SI window of the requested SIB in one or more SI periods of the SIB. Scheduling information for other SIs, including SIB type, validity information, periodicity, SI window information, may be provided at the minimum SI, regardless of whether other SIs are periodically broadcast or provided on demand. In one embodiment, the UE first checks the SI response window for SI response and, if not received, it monitors the SI window to receive the requested SI.

Fig. 12 illustrates a method for indicating whether other system information is broadcast in basic system information that is broadcast according to another embodiment of the present disclosure.

Referring to fig. 12, in another embodiment of the present disclosure, system information (in addition to basic system information) may also be broadcast by the BS. As shown in fig. 12, the BS may indicate whether other system information is broadcast in the broadcasted basic system information.

In operation S1210, the BS periodically broadcasts minimum/basic system information (e.g., sets SI _ TX _ Indication to zero). In one embodiment, the indication may be specific to the SI or set of SIs or service (an indication to request system information or an indication that system information is broadcast).

In response to the SI _ TX _ Indication, the UE transmits an SI request/PRACH-SI to acquire other system information in operations S1220 and S1230. SI request/PRACH-SI is specific to SI or a set or service of SIs. In operation S1240, the BS transmits an SI-response/RAR-SI including the requested system information in response to the PRACH-SI.

If the system information is not broadcast, the UE may request using the previously explained method (FIG. 11). If broadcasted, the UE reads the broadcasted system information to acquire required system information. In case the PRACH-SI information is broadcast for on-demand signaling, i.e. for requesting system information, the absence of said information in the broadcasted basic system information may indicate that the UE may read the system information from the broadcast signaling. In the case where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast (e.g., set SI _ TX _ Indication to one), and the small cell may indicate that system information is not broadcast (e.g., set SI _ TX _ Indication to zero).

In another embodiment of the present disclosure, the BS may also indicate the supported SI in the basic system information. The UE may then request one or more supported SIs using the previously explained method (fig. 1).

Fig. 13 illustrates a method for acquiring system information according to another embodiment of the present disclosure.

Referring to fig. 13, in the method of the present disclosure, a UE may acquire system information, as shown in fig. 13. System information is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information that is periodically broadcast by a cell and/or TRP. The second category (also referred to as other SIs) includes one or more common system information that is provided to the UE on demand or that may be broadcast periodically.

In this method, the BS broadcasts a first type (also referred to as minimum SI or basic SI) of system information. In operation S1310, the UE acquires first-type (also referred to as minimum SI or basic SI) system information from the broadcast information.

In another example, if there are several requests for on-demand system information, the network may start broadcasting system information instead of providing system information on-demand. The minimum SI or the basic SI may include an indication that all SIs of the second type of system information are periodically broadcast or provided on demand. Alternatively, the minimum SI or basic SI may include a separate indication for each SI (e.g., SIB) or set of SIs (i.e., SIBs), where each indication indicates whether to periodically broadcast or provide the associated SI or set of SIs on demand.

Alternatively, the minimum SI or the basic SI may include a separate indication for each SI message, where each SI message carries one or more SIs (i.e., SIBs). The indication associated with the SI message indicates whether to broadcast or provide the SI associated with the SI message on an as-needed basis. The mapping of SI messages to SIBs is included in the minimum SI or the basic SI. To acquire the second type SI, the UE first determines whether to broadcast the SI periodically or to provide the SI on demand. The UE determines this based on an indication included in the first type (also referred to as minimum SI or basic SI) of system information. If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is periodically broadcast (or not provided on demand), the UE acquires the SI from the periodic broadcast using scheduling information included in the first type (also referred to as minimum SI or basic SI).

In operation S1320, if the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is not regularly broadcasted (or provided on demand), the UE transmits a request to the BS to receive the SI. Alternatively, the BS may transmit the SI in a RAR message in operation S1330.

In this method, the BS also broadcasts scheduling information regarding other system information. However, other system information is not broadcast periodically. In operations S1340 and S1350, the BS broadcasts other system information for a defined time period upon receiving a trigger (e.g., PRACH-SI) from the UE. The trigger may be specific to system information or a set of system information or a service or a UE type. During the time period in which the system information is broadcast after receiving the trigger from the UE, the BS may broadcast an indication that it is broadcasting the system information. The indication may be specific to system information or a set of system information or a service or a UE type. This ensures that other UEs do not trigger the PRACH-SI and are able to read system information from the broadcast. The trigger for the broadcast may be sent at a time slot configured by the network. In one embodiment, the trigger for the broadcast may be sent once relative to the location of the particular system information. In operation S1360, the BS broadcasts and the UE acquires the basic SI. In operation S1370, the BS broadcasts and the UE acquires the SI, and the location of the SI may be indicated in the basic SI.

Fig. 14 illustrates a method for acquiring system information according to another embodiment of the present disclosure. In the method of the present disclosure, the UE may acquire system information, as shown in fig. 14.

Referring to fig. 14, in the method of the present disclosure, a UE may acquire system information, as shown in fig. 14. System information is divided into two categories: the first class (also referred to as minimum SI or basic SI) includes one or more system information that is periodically broadcast by a cell and/or TRP. The second category (also referred to as other SIs) includes one or more common system information that is provided to the UE on demand or that may be broadcast periodically.

The first class includes basic system information such as information required for initial access to a cell, information required for acquisition of system information in the second class. The second type of system information includes system information not included in the first type. In this method, the BS broadcasts a first type (also referred to as minimum SI or basic SI) of system information. In operation S1410, the UE acquires first-type (also referred to as minimum SI or basic SI) system information from the broadcast information.

Whether the system information in the second category is broadcast periodically or provided on demand, the network signal is in the first category of system information, i.e., in the minimum SI or the basic SI. For example, where the heterogeneous network includes a macro cell and a small cell, the macro cell may indicate that system information is broadcast, while the small cell may indicate that system information is not broadcast. In another example, if there are several requests for on-demand system information, the network may start broadcasting system information instead of providing system information on-demand.

The minimum SI or the basic SI may include an indication that the SI indicating the second type of system information is periodically broadcast or provided on demand. Alternatively, the minimum SI or basic SI may include a separate indication for each SI (e.g., SIB) or set of SIs (i.e., SIBs), where each indication indicates whether to periodically broadcast or provide the associated SI or set of SIs on demand. Alternatively, the minimum SI or the basic SI may include a separate indication for each SI message, where each SI message carries one or more SIs (i.e., SIBs). The indication associated with the SI message indicates whether to broadcast or provide the SI associated with the SI message on an as-needed basis. The mapping of SI messages to SIBs is included in the minimum SI or the basic SI.

To acquire the second type SI, the UE first determines whether to broadcast the SI periodically or to provide the SI on demand. The UE determines this based on an indication included in the first type (also referred to as minimum SI or basic SI) of system information. If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is periodically broadcast (or not provided on demand), the UE acquires the SI from the periodic broadcast using scheduling information included in the first type (also referred to as minimum SI or basic SI). If the first type (also referred to as minimum SI or basic SI) of system information indicates that the SI that the UE wants to acquire is not regularly broadcasted (or provided on demand), the UE sends a request to the BS to receive the SI.

In order to acquire one or more SIs provided on demand, if the UE is in an RRC idle state, the UE performs an RRC connection setup procedure in operation S1420. In the RRC connected state, the UE transmits an SI request message in operation S1430. The SI request message indicates one or more sets of system information needed by the UE, or indicates a service (e.g., eMBB, MTC, URLL, etc.) or UE type that the UE needs the system information. The UE may send its UE ID (i.e., S-TMSI, C-RNTI, RA-RNTI, etc.) along with the SI request message.

In response to the SI request, the BS transmits an SI response in operation S1440, wherein the SI response includes the requested system information. The scheduling control information indicating the SI response may be masked with the ID of the UE (e.g., C-RNTI, RA-RNTI) or a predefined ID (e.g., SI-RNTI). The predefined ID may be different for different system information or system information sets or services or UE types.

The UE may indicate the required system information in the SI-request using the mechanism explained in method 1.

In one embodiment, the SI request may be included in an RRC connection request and the SI response may be included in an RRC connection response. In another embodiment, the BS may determine system information required by the UE based on services supported by the UE or based on services to which the UE has requested connection, and provide the system information to the UE using dedicated signaling.

In one embodiment, the eNB may provide the requested system information for one or more cells. The ENB may indicate a cell to which the system information provided in the SI response is applicable. Therefore, when the UE changes cells, the UE does not need to request system information. After the cell change, if the UE does not have system information of the new cell, the UE requests the system information.

Fig. 15 illustrates a method for acquiring system information according to another embodiment of the present disclosure.

Referring to fig. 15, in the method of the present disclosure, a UE may acquire system information, as shown in fig. 15. In operation S1510, the BS (or 5G cell) broadcasts a synchronization signal, i.e., PSS/SSS. No system information is broadcast periodically.

To request SI, the UE transmits a PRACH-SI preamble in operation S1520. The PRACH-SI preamble may be predefined. The time and frequency resources of the PRACH-SI transmission may be defined with respect to the PSS/SSS. Upon receiving the PRACH-SI preamble, the BS may broadcast minimum SI or system information or common system information in operation S1530. If no system information is broadcast, the UE may use the previously explained method for acquisition.

In the previously explained method, the UE requests system information on demand in the disclosed network, which can configure the time period the UE can request. This may reduce the number of requests.

If the response is broadcast, it may be in a time window relative to the time the request was sent. In the previously explained method, the UE requests system information on demand, and the UE may monitor broadcast transmissions during a defined time before requesting the required system information to receive the required system information.

Fig. 16 illustrates a method for providing system information within a time window according to an embodiment of the present disclosure.

Referring to fig. 16, after sending the SI request, one or more SIBs requested by the UE are provided within some time window (i.e., an SI response window). After sending the SI request, the UE listens to the NR-PDCCH in the SI response window in order to receive the requested SIB. The UE may retransmit the SI request if the UE does not receive the requested SIB within the SI response window.

In one embodiment, the length of the SI response window is provided in the Mobile Subscriber Identity (MSI) (basic system information). In another embodiment, the acknowledgement of the SI request may be performed when the UE checks the RAR after sending the SI request or the UE checks an indication in the MSI.

Fig. 17 illustrates a method for providing system information by monitoring a time window for one or more periods, according to an embodiment of the present disclosure.

Referring to fig. 17, after sending the SI request, to receive the requested SIB, the UE monitors the SI window of the requested SIB in one or more SI periods of the SIB. Scheduling information of other SIs including SIB type, validity information, periodicity, SI window information is in the minimum SI, regardless of whether other SIs are periodically broadcast or provided on demand.

In one embodiment, the acknowledgement of the SI request may be performed when the UE checks the RAR after sending the SI request or the UE checks an indication in the MSI.

Minimizing SI reacquisition

There may be several small cells within the coverage of the macro cell. Currently, the system information is cell-specific. Currently, each cell (small cell as well as macro cell) transmits its own system information. In embodiments of the present disclosure, a first cell (e.g., a macro cell) provides information about one or more second cells (e.g., small cells).

The multiple system information parameters may have the same value across many cells. Thus, in one embodiment, the system information parameters may be classified into cell-specific information and non-cell-specific information. The non-cell specific information, i.e. the system information having a common value across one or more second cells (e.g. small cells), may be signaled using signalling broadcast or dedicated by the first cell (e.g. macro cell) or may be provided on demand. Cell specific information is signaled by each cell.

In one embodiment, the first cell may signal several sets of system information using broadcast or dedicated signaling. In one embodiment, each of these sets may be indexed in the order in which they are signaled by the first cell. The second cell may indicate (using broadcast or dedicated signalling) which set of system information among the plurality of sets signalled by the first cell applies to that cell. In an alternative embodiment, the first cell may indicate the cell id of the cell and a list for each set, where the cell id identifies the cell to which the set applies.

In an embodiment, cell-specific system information may be obtained as follows:

option 1: UE acquisition from macro cell

1 a. the macro cell broadcasts this information in the broadcast signalling.

1b the macro cell provides this information in dedicated signalling.

The macro cell may indicate whether it uses broadcast signaling to provide such information.

If such information is not broadcast, the macro cell may also indicate whether it provides such information in dedicated signaling.

On-demand signaling as explained previously may also be used to request information from the macro cell.

Option 2: UE acquisition directly from cell

If the macro cell does not provide information, the UE acquires directly from the cell.

The small cell may broadcast this information.

On-demand signaling as explained previously may be used to request information from the cell.

In the previously explained method, system information received from a cell from a periodic broadcast or using the previously explained on-demand SI request procedure may be used for one or more cells. The cell from which the received system information may be used may be indicated by the cell from which the system information is acquired from a periodic broadcast or using the previously explained on-demand SI request procedure. The UE may also receive system information from multiple cells from a periodic broadcast or using an on-demand SI request procedure. Therefore, when the UE changes cells, the UE does not need to request or reacquire system information. After the cell change, if the UE does not have system information of the new cell, the UE reacquires or requests the system information.

Fig. 18 illustrates a method for configuring a system information area ID according to an embodiment of the present disclosure.

Referring to fig. 18, in an alternative embodiment, a system information area concept may be defined. The system information area refers to an area covering one or more cells or transmission points or transmission/reception points (where the same of the system information is used). The system information area may be identified by a system information area identifier. A cell or transmission point or transmission/reception point broadcasts a system information area identifier.

When a UE moves from one cell to another, it checks the SI area ID. If there is a change in the SI area ID, the UE reacquires the system information. For example, as shown in fig. 18, if the UE moves from cell 1 to cell 3, there is no need to reacquire system information. If the UE moves from cell 1 to cell 8, it needs to reacquire the system information.

In embodiments of the present disclosure, the system information area (or SI area ID) may be different for different SIs (or SIBs). In embodiments of the present disclosure, the system information area (or SI area ID) may be different for different SI Sets (SIBs). In an embodiment of the present disclosure, one system information area (or SI area ID) may be used for SI (or SIB). In embodiments of the present disclosure, some SIs are cell-specific and SI area IDs are not associated with them.

In embodiments of the present disclosure, different versions of associated SI may be used within an SI region. Each of these versions is identified by an index or value tag. Assume that the SI regions for SIB X are as shown in fig. 16. Cell 1, cell 2 and cell 3 use the configuration of SIBx. Cell 1, cell 2 and cell 3 broadcast for SIBx with SI area ID of 1 and index/value label of P. If cell 1, cell 2 and cell 3 want to use different configurations for SIBx, they broadcast for SIBx with SI area ID of 1 and index/value tag of Q. Within the same SI area, if there is a change in index or value tag and the UE does not have a valid SI configuration corresponding to the new index/value tag of the SI area, the UE reacquires the corresponding SI. The SI configuration identified by the index/value tag is valid in the SI area where it is acquired. It is not valid in another SI area. The valid range of index/value tags is within the SI region. For example, the configuration of SIBx identified by index/value tag P in SI area ID 1 is different from the configuration of SIBx identified by index/value tag P in SI area ID 2 or SI area ID 3. It should be noted that in the prior art, the range of value tags is one cell. In the method of the present disclosure, the range of the value tag is an SI region, i.e., a plurality of cells.

Fig. 19 illustrates a method for indexing system information parameters according to an embodiment of the present disclosure.

Referring to fig. 19, in an embodiment of the present disclosure, a BS may support a set of a plurality of configuration values of system information parameters. For example, assume that SI includes parameters P, Q and R. It is assumed that the parameter P may have values P0, P1. The parameter Q may have values Q0, Q1, Q2. The parameter R may have values R0, R1. For these parameters, there may be 12 possible configurations, 2 × 3 × 2 ═ 12, where each configuration has a different value of at least one parameter from the other configurations. Each of these configurations is assigned an index. The index may be signaled instead of the parameters and their values (in broadcast or dedicated signaling). For example, configuration 0: p- > P0, Q- > Q0, R- > R0; configuration 1: p- > P0, Q- > Q1, R- > R0; and so on.

For SI with parameters A, B and C, a set of possible configurations is shown in fig. 19. In this example, parameter a may have two possible values a0 and a 1. The parameter B may have two possible values B0 and B1. The parameter C may have two possible values C0 and C1. Note that each parameter may have a different number of values. Each path from top to bottom in the tree (fig. 16) is an efficient configuration. As shown in fig. 16, these configurations may be numbered in order. The 8 possible configurations are as follows:

idx 0: { a0, B0, C0 }; idx 1: { a0, B0, C1 }; idx 2: { a0, B1, C0 }; idx 3: { a0, B1, C1 }; idx 4: { a1, B0, C0 }; idx 5: { a1, B0, C1 }; idx 6: { a1, B1, C0 }; idx 7: { a1, B1, C1 }; idx ═ index of values of parameter a (number of values of B × (number of values of C) } + { index of values of parameter B × (number of values of C) } + index of values of parameter C. To allow skipping of parameters in the configuration, skipping may be considered as an additional value. For example, if parameter a can be skipped, parameter a may have three values a0, a1, skip. The a0 value has an index of 0, the a1 value has an index of 1, and the skip value has an index of 2.

If the possible values for each SI parameter are known and then given an index, then the configuration corresponding to the index can be known. The SI may be classified into various parts/groups, etc., where each part or group has its own configuration index. Each SI part or SI group may have several configurations, and each configuration may be indicated using an index as shown above. For example, assume that there are two SI parts, SI part 1 and SI part 2. SI part 1 has three parameters A, B, C. The SI part has two parameters P, Q. The SI part 1 configuration and the SI part 2 configuration may be independently indicated using their own configuration indexes.

The configuration index may be broadcast or signaled using dedicated signaling. If SI is requested on demand, a configuration index may be signaled in response rather than a full configuration. Alternatively, the configuration index of the SI may be broadcast. If the UE cannot know the configuration based on the broadcast index, it can request the BS/eNB/TRP to provide the configuration corresponding to the index by sending the index in the SI request. If the UE does not know the values of the parameters supported in the cell/BS/eNB/TRP, it may not know the index-based configuration. For example, parameter a may have values a0, a1, a2, and A3. But the values a0, a1 may be supported in cell 1 and the values a2, A3, a1 may be supported in another cell 2. If the UE cannot know the configuration based on the broadcast index, it may request the BS/eNB/TRP to provide parameter values of the SI supported in the cell/BS/eNB/TRP in the SI request. Once the parameter values of the supported SI in the cell/BS/eNB/TRP are known, the UE may determine the configuration corresponding to the broadcast index. The SI request/response may be signaled using the previously explained method.

The parameter values of the supported SI may be the same throughout the network or may be cell/TRP specific. The parameter values of the supported SI part/group may be the same throughout the network and for other SI parts/groups it may be cell/TRP specific.

In another embodiment, instead of indices as shown in fig. 19, the network or cell/TRP/eNB may maintain several configurations of SI or SI parts or SI groups and assign a different index/identifier to each configuration. The network indicates the index/identifier for each SI or SI part/group in the broadcast signaling. The UE first receives the broadcast signaling and acquires the index/identifier for the SI or SI part/group. If the UE does not have the configuration corresponding to the index/identifier, the UE requests the configuration corresponding to the index/identifier using the previously explained on-demand signaling. The index/identifier may be included in the request. If the UE has a valid configuration corresponding to the index/identifier, then the UE uses it and does not need a request. Note that in one embodiment, the index/identifier may be valid across cells or TRPs or enbs for SI or SI portions of an SI group. In another embodiment, the index/identifier may be valid across TRPs of the same cell for SI or SI part of an SI group. Whether the index/identifier for an SI or SI part or SI group is valid across cells or TRPs or enbs or the like may be predefined or indicated in the broadcast signaling. The UE may store the configuration corresponding to the index/identifier for a defined lifetime.

Fig. 20 illustrates a method for configuring a system information configuration ID according to an embodiment of the present disclosure.

Referring to fig. 20, when a UE moves from one cell to another, the UE reacquires SI if there is a change in the index of the SIB and it does not have a configuration corresponding to the index used in the cell, and otherwise does not reacquire SI. As shown in fig. 18, assume that three configurations identified by index X, Y, Z are used for the SIB X network. If the UE moves from cell 1 to cell 3, there is no need to reacquire SIBx, since both cells use the same configuration. If the UE moves from cell 1 to cell 2, the SIBx must be reacquired if the UE does not have the stored configuration corresponding to index x. Unlike previous approaches, the range of indices is the entire network rather than the SI area. The index may also be named value tag, where the range of value tags is the entire network rather than one cell.

System information update program

The UE may be notified of the system information update by one of:

option 1

The system information is classified into various parts/groups/sets. The BS broadcasts the supported system information set. The BS also broadcasts a value tag/identifier/configuration index for each supported system information set/part/group. A change in the value tag/identifier/configuration index corresponding to the system information set indicates that the system information set/group/part is updated. In addition, the BS may also broadcast a change notification for each system information of the service. Or

The BS broadcasts the supported services. The BS also broadcasts a value tag/identifier/configuration index for each supported service. A change in the value tag/identifier/configuration index corresponding to a service indicates that system information for the service is updated. In addition, the BS may also broadcast a change notification for each system information of the service.

Option 2

A change notification for each supported system information set or service is indicated in the paging message. The value tag/identifier/configuration index associated with the updated system information may also be indicated in the paging message.

Option 3

The change notification may be indicated using an SI update message.

Each SI update message may indicate notification of a group of SIs. The group-specific RNTI may be used to schedule the SI update message.

The SI update message may be an RRC message or DCI signaled in the PDCCH.

Obtaining update information

If an update indication is received using the previously explained method (i.e. broadcast or on demand), the UE requests an updated set of system information or service specific system information. If the changed system information set is part of the broadcast information, the UE acquires updated system information from the broadcast. If the changed system information set is part of the on-demand system information, the UE uses on-demand signaling to acquire updated system information.

And (3) Alt: the Network (NW) may broadcast the updated information for a defined period of time. The UE reads the broadcasted information.

In one embodiment, the value tag/identifier/configuration index may indicate that the system information set/group/portion is changed. In another embodiment, the value tag/identifier/configuration index may identify a particular configuration of a system information set/group/portion. When the network signals a system information set/group/part identifier and the UE does not have a configuration corresponding to said identifier, then the UE updates the system information. In one embodiment, each of the SI sets/portions/groups may contain the same parameters, but may be valid in different regions.

While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.

Claims

1. A method performed by a terminal in a wireless communication system, the method comprising:

receiving, from a base station, a system information first SI that is periodically broadcast, the first SI including information indicating whether a second SI different from the first SI is being broadcast;

sending a Physical Random Access Channel (PRACH) lead code to the base station;

receiving a random access response, RAR, from the base station as a response to the PRACH preamble, the RAR comprising an uplink, UL, grant for an SI request message;

based on the information in the first SI indicating that the second SI is not being broadcast, sending an SI request message to the base station requesting a second SI based on the UL grant; and

receiving the requested second SI from the base station based on the SI request message.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of a red light source, a green light source, and a blue light source,

wherein scheduling information for the requested second SI is monitored within a time window,

wherein the scheduling information is masked by a system information radio network temporary identifier SI-RNTI, and

wherein a length of the time window is identified based on the first SI.

3. The method of claim 1, wherein the SI request message includes a list of SIs needed by the terminal.

4. The method of claim 1, wherein the first SI comprises an SI area Identifier (ID) for an area comprising one or more cells applying the second SI.

5. A method performed by a base station in a wireless communication system, the method comprising:

transmitting a first System Information (SI) including information indicating whether a second SI different from the first SI is being broadcast to a terminal by periodically broadcasting the first SI;

receiving a Physical Random Access Channel (PRACH) preamble from the terminal;

sending a random access response, RAR, to the terminal as a response to the PRACH preamble, the RAR including an uplink, UL, grant for an SI request message;

receiving an SI request message for requesting a second SI from the terminal based on the UL grant based on the information in the first SI indicating that the second SI is not being broadcast; and

transmitting the requested second SI to the terminal based on the SI request message.

6. The method of claim 5, wherein the first and second light sources are selected from the group consisting of a red light source, a green light source, and a blue light source,

wherein the scheduling information for the requested second SI is transmitted within a time window,

wherein a length of the time window is identified based on the first SI.

7. The method of claim 5, wherein the SI request message comprises a list of SIs required by the terminal.

8. The method of claim 5, wherein the first SI comprises an SI area Identifier (ID) for an area comprising one or more cells applying the second SI.

9. A terminal in a wireless communication system, the terminal comprising:

a transceiver; and

a controller configured to:

receiving, via the transceiver, a periodically broadcast System Information (SI) from a base station, the SI including information indicating whether a second SI different from the first SI is being broadcast,

transmitting a Physical Random Access Channel (PRACH) preamble to the base station via the transceiver,

receiving, via the transceiver, a random access response, RAR, from the base station as a response to the PRACH preamble, the RAR comprising an uplink, UL, grant to an SI request message,

based on the information in the first SI indicating that the second SI is not being broadcast, sending, via the transceiver, an SI request message to the base station requesting a second SI based on the UL grant, and

receiving, via the transceiver, the requested second SI from the base station based on the SI request message.

10. The terminal according to claim 9, wherein the terminal further comprises a receiver,

wherein a length of the time window is identified based on the first SI.

11. The terminal of claim 9, wherein the SI request message includes a list of SIs needed by the terminal.

12. The terminal of claim 9, wherein the first SI comprises an SI area identifier, ID, for an area comprising one or more cells to which the second SI is applied.

13. A base station in a wireless communication system, the base station comprising:

a transceiver; and

a controller configured to:

transmitting, via the transceiver, a first System Information (SI) to a terminal by periodically broadcasting the first SI, the first SI including information indicating whether a second SI different from the first SI is being broadcast,

receiving a physical random access channel, PRACH, preamble from the terminal via the transceiver,

transmitting a random access response, RAR, to the terminal via the transceiver as a response to the PRACH preamble, the RAR comprising an uplink, UL, grant to an SI request message,

based on the information in the first SI indicating that the second SI is not being broadcast, receiving an SI request message from the terminal via the transceiver requesting a second SI based on the UL grant, and

transmitting the requested second SI to the terminal via the transceiver based on the SI request message.

14. The base station of claim 13, wherein the base station is further configured to,

wherein a length of the time window is identified based on the first SI.

15. The base station of claim 13, wherein the SI request message includes a list of SIs needed by the terminal.

16. The base station of claim 13, wherein the first SI comprises an SI area identifier, ID, for an area comprising one or more cells to which the second SI is applied.